With the development of the world economy, industrial production and transportation etc. are depending higher and higher on oil, and the following environmental issues such as the greenhouse effect, ecological deterioration become increasingly severe. How to maintain the harmonious development between economy and environment has become the focus of the global concerns. The conventional RTG in terminals uses one generator set as the power and the fuel efficiency is less than 30%. Main reasons are as follows:                a) Large installed capacity: to meet the short-time highest load demand of RTG, the power of the generator set must be designed according to the maximum demand of RTG, about eight times larger than the average power while the RTG is under actual operations,        b) Low fuel efficiency: when the generator set is running in the best economical fuel consumption area, the best energy efficiency is received. To ensure the normal power for the controlling system and the operating mechanism, the output power of the generator set must be higher than the power demand of RTG while the RTG is working. The generator set should run at the rated speed continuously. Due to the different power demands under different working conditions of RTG, real-time adjustment of output power for the generator set is required to match the power demand of RTG. Therefore, most of the time the generator set is running off the best economical fuel consumption area, and the energy efficiency is low. As shown in section A of the fuel consumption characteristics loop image in FIG. 2, when the generator set is running under the rotational speed of 1200-1300 RPM and the output power is about 240 kW, the fuel consumption rate is lowest to 186 g/kWh which is called “the best economical fuel consumption area”. When the system power demand reduces to below 40 kW, the fuel consumption rate reaches up to 426 g/kWh (section B in FIG. 2), which is 2.3 times of the best economical fuel consumption rate. When the RTG is accelerating speed with heavy load while lifting, black smoke and serious pollution will be caused by poor fuel combustion of engine.        c) No function for recovery of braking energy: when the hoisting mechanism of RTG is declining, the trolley travelling mechanism and the cranes travelling mechanism are decelerating and braking, since there are no energy storing devices, all the feedback energy has to be consumed through power resistors in real time.        